#!/bin/bash

# Media Library FLAC Downsampling Script
# Processes multiple albums in a media library, downsampling all FLAC files to 44.1 kHz

# Check if ffmpeg is installed
if ! command -v ffmpeg &> /dev/null; then
    echo "Error: ffmpeg is not installed or not in PATH"
    exit 1
fi

# Function to display usage
show_usage() {
    echo "Usage: $0 [OPTIONS] <media_library_path>"
    echo ""
    echo "Options:"
    echo "  -o, --output DIR     Output directory (default: creates _44k suffix)"
    echo "  -r, --replace        Replace original files (use with caution)"
    echo "  -p, --preserve       Preserve original files alongside new ones"
    echo "  -t, --test           Test mode - show what would be processed"
    echo "  -h, --help           Show this help message"
    echo ""
    echo "Examples:"
    echo "  $0 /path/to/music/library"
    echo "  $0 -o /path/to/output /path/to/music/library"
    echo "  $0 --test /path/to/music/library"
    echo "  $0 --replace /path/to/music/library"
}

# Default options
OUTPUT_DIR=""
REPLACE_MODE=false
PRESERVE_MODE=false
TEST_MODE=false
PROCESSED_COUNT=0
SKIPPED_COUNT=0
ERROR_COUNT=0

# Parse command line arguments
while [[ $# -gt 0 ]]; do
    case $1 in
        -o|--output)
            OUTPUT_DIR="$2"
            shift 2
            ;;
        -r|--replace)
            REPLACE_MODE=true
            shift
            ;;
        -p|--preserve)
            PRESERVE_MODE=true
            shift
            ;;
        -t|--test)
            TEST_MODE=true
            shift
            ;;
        -h|--help)
            show_usage
            exit 0
            ;;
        -*)
            echo "Unknown option: $1"
            show_usage
            exit 1
            ;;
        *)
            MEDIA_LIBRARY="$1"
            shift
            ;;
    esac
done

# Check if media library path is provided
if [ -z "$MEDIA_LIBRARY" ]; then
    echo "Error: Media library path is required"
    show_usage
    exit 1
fi

# Check if media library exists
if [ ! -d "$MEDIA_LIBRARY" ]; then
    echo "Error: Media library directory '$MEDIA_LIBRARY' not found"
    exit 1
fi

# Set output directory if not specified
if [ -z "$OUTPUT_DIR" ] && [ "$REPLACE_MODE" = false ]; then
    OUTPUT_DIR="${MEDIA_LIBRARY}_44k"
fi

# Function to check if file needs downsampling
needs_downsampling() {
    local file="$1"
    
    # Check if file is readable
    if [ ! -r "$file" ]; then
        echo "    WARNING: File not readable: $file"
        return 1
    fi
    
    local sample_rate=$(ffprobe -v quiet -select_streams a:0 -show_entries stream=sample_rate -of csv=p=0 "$file" 2>/dev/null)
    
    if [ -z "$sample_rate" ]; then
        echo "    WARNING: Could not determine sample rate for: $(basename "$file")"
        return 1  # Skip files we can't analyze
    elif [ "$sample_rate" = "44100" ]; then
        return 1  # No downsampling needed
    else
        echo "    Current sample rate: ${sample_rate} Hz"
        return 0  # Needs downsampling
    fi
}

# Function to process a single FLAC file
process_flac_file() {
    local input_file="$1"
    local relative_path="$2"
    local output_file=""
    
    # Determine output file path
    if [ "$REPLACE_MODE" = true ]; then
        output_file="$input_file"
    elif [ "$PRESERVE_MODE" = true ]; then
        local dir=$(dirname "$input_file")
        local filename=$(basename "$input_file" .flac)
        output_file="$dir/${filename}_44k.flac"
    else
        output_file="$OUTPUT_DIR/$relative_path"
    fi
    
    # Check if downsampling is needed
    if ! needs_downsampling "$input_file"; then
        echo "  SKIP: $relative_path (already 44.1 kHz)"
        ((SKIPPED_COUNT++))
        return
    fi
    
    if [ "$TEST_MODE" = true ]; then
        echo "  WOULD PROCESS: $relative_path → $(basename "$output_file")"
        return
    fi
    
    # Create output directory if needed
    local output_dir=$(dirname "$output_file")
    if [ ! -d "$output_dir" ]; then
        echo "    Creating directory: $output_dir"
        if ! mkdir -p "$output_dir"; then
            echo "  ✗ ERROR: Cannot create output directory: $output_dir"
            ((ERROR_COUNT++))
            return
        fi
    fi
    
    # Verify input file exists and is readable
    if [ ! -f "$input_file" ]; then
        echo "  ✗ ERROR: Input file not found: $input_file"
        ((ERROR_COUNT++))
        return
    fi
    
    if [ ! -r "$input_file" ]; then
        echo "  ✗ ERROR: Input file not readable: $input_file"
        ((ERROR_COUNT++))
        return
    fi
    
    # Create temporary file for safe processing (use .flac extension)
    local temp_file="${output_file}.tmp.flac"
    
    echo "  PROCESSING: $relative_path"
    
    # Downsample the file
    echo "    Command: ffmpeg -i \"$input_file\" -ar 44100 -c:a flac -compression_level 8 -y \"$temp_file\""
    
    if ffmpeg -i "$input_file" -ar 44100 -c:a flac -compression_level 8 -y "$temp_file" 2>"${temp_file}.log"; then
        # Move temp file to final location
        mv "$temp_file" "$output_file"
        echo "  ✓ DONE: $(basename "$output_file")"
        rm -f "${temp_file}.log"
        ((PROCESSED_COUNT++))
    else
        echo "  ✗ ERROR: Failed to process $relative_path"
        echo "    Error log saved to: ${temp_file}.log"
        if [ -f "${temp_file}.log" ]; then
            echo "    Last few lines of error:"
            tail -n 5 "${temp_file}.log" | sed 's/^/    /'
        fi
        rm -f "$temp_file"
        ((ERROR_COUNT++))
    fi
}

# Function to process an album directory
process_album() {
    local album_dir="$1"
    local album_name=$(basename "$album_dir")
    
    echo "Processing album: $album_name"
    
    # Find all FLAC files in the album directory
    local flac_files=()
    while IFS= read -r -d '' file; do
        flac_files+=("$file")
    done < <(find "$album_dir" -name "*.flac" -type f -print0)
    
    if [ ${#flac_files[@]} -eq 0 ]; then
        echo "  No FLAC files found in $album_name"
        return
    fi
    
    # Process each FLAC file
    for flac_file in "${flac_files[@]}"; do
        local relative_path="${flac_file#$MEDIA_LIBRARY/}"
        process_flac_file "$flac_file" "$relative_path"
    done
    
    echo ""
}

# Main processing
echo "Media Library FLAC Downsampler"
echo "==============================="
echo "Input:  $MEDIA_LIBRARY"

if [ "$TEST_MODE" = true ]; then
    echo "Mode:   TEST MODE (no files will be modified)"
elif [ "$REPLACE_MODE" = true ]; then
    echo "Mode:   REPLACE (original files will be overwritten)"
elif [ "$PRESERVE_MODE" = true ]; then
    echo "Mode:   PRESERVE (44k files created alongside originals)"
else
    echo "Output: $OUTPUT_DIR"
fi

echo ""

# Find all directories that contain FLAC files (potential albums)
album_dirs=()
while IFS= read -r -d '' dir; do
    if find "$dir" -maxdepth 1 -name "*.flac" -type f | grep -q .; then
        album_dirs+=("$dir")
    fi
done < <(find "$MEDIA_LIBRARY" -type d -print0)

if [ ${#album_dirs[@]} -eq 0 ]; then
    echo "No albums with FLAC files found in $MEDIA_LIBRARY"
    exit 0
fi

echo "Found ${#album_dirs[@]} album(s) with FLAC files"
echo ""

# Process each album
for album_dir in "${album_dirs[@]}"; do
    process_album "$album_dir"
done

# Summary
echo "Processing Summary:"
echo "=================="
echo "Processed: $PROCESSED_COUNT files"
echo "Skipped:   $SKIPPED_COUNT files (already 44.1 kHz)"
echo "Errors:    $ERROR_COUNT files"

if [ "$ERROR_COUNT" -gt 0 ]; then
    exit 1
fi